1. Field of the Invention
The present invention relates to a compound semiconductor deposition method of depositing a compound semiconductor of a ternary or higher system on a substrate by using photo CVD, thermal CVD, MBE or the like.
2. Description of the Related Art
Attention has been paid to gallium nitride compound semiconductors of a ternary or higher system, such as indium gallium nitride (InGaN) having In blended in gallium nitride (GaN) and gallium aluminum nitride (GaAlN) having Al blended in GaN, as semiconductor materials for monochromatic LEDs having arbitrary luminous wavelengths like wavelengths of blue light and white light (see, for example, Patent Document 1).
When the luminous wavelength of such a compound semiconductor of a ternary or higher system which constitutes an LED shifts even by 1 nm, the color tone (or hue) of an RGB image obtained as a consequence changes. With the aforementioned InGaN as an example of the compound semiconductor of a ternary or higher system used for an LED, the luminous wavelength of InGaN changes according to the blend ratio of In into GaN. While the luminous wavelength of GaN is about 400 nm, for example, the luminous wavelength of InN is about 1.5 μm. That is, in case of the InGaN, a compound semiconductor with a desired luminous wavelength in the range of the wavelength band of 400 nm to 1.5 μm can be obtained according to the blend ratio of In. When the blend ratio of In slightly changes, on the other hand, the luminous wavelength of a compound semiconductor to be obtained changes significantly.
Conventionally, the blend ratio of In cannot be controlled with high accuracy, so that a deviation of the luminous wavelength in a nanometer-order cannot be overcome. This makes it difficult to improve the yield of LEDs to be manufactured.